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Re: Science feather strength debate



Jason Brougham <jaseb@amnh.org> wrote:


> Yeah, also, what exactly is the aerodynamic function of tertials? A wing
> is not a sail or a  parachute. The feathers closest to the armpit move the
> slowest and the least far during a flap, so do they even generate any
> lift?


Yes, during flight the tertiaries "fill the space" between the body
wall and the secondaries.  In doing so, they allow a continuous flight
surface to be maintained, and thereby increase the lift-to-drag ratio
of the wing.  Because the humeral shaft tends to be quite short in
extant birds (relative to the distal elements), not many tertiaries
are needed.


Also, when the wing is folded, tertiaries cover the secondary remiges
(which  in turn cover the primaries), so they have a protection
function.


Augusto Haro <augustoharo@gmail.com> wrote:

> Agreeing with your opinion, as far as I am aware, as the bird humerus
> is surrounded by muscle in a greater measure than the ulna, it is to
> be expected that the plumage is not so firmly attached to the skeleton
> at this point, and it may thus be more easily disarticulated with
> decay. Correct me if I am wrong, but I never read or saw first-hand
> humeri with feather knobs, while they can be found in the
> carpometacarpus in addition to the ulna. If true, the lack of these
> feather attachment structures may suggest feathers were not attached
> to the humerus.


Yes, that's my understanding too, Augusto.


Cheers

Tim